Method and apparatus for controlling the temperature of briquetting rolls



July 6, 1965 J. R. GUSEMAN ETAL 3,193,377

METHOD AND APPARATUS FOR CONTROLLING THE TEMPERATURE OF BRIQUETTINGROLLS Filed April 12, 1962 CONTROL I CON TROL 35 35 29 29 Q 33 INVENTORJAMES R. GUSEMA/V and DONALD E. ROHAUS A ffarney United States Patent3,193,377 NETHOD AND APPARATU FOR CONTROLLING THE TEMPERATURE ()FBRIQUETTING ROLLS James R. Gusernan, Irwin, and Donaid E. Rohaus,Monroeviile, Pa., assignors to United States Steel Corporation, acorporation of New Jersey Filed Apr. 12, 1952, der. No. 186,902 8Claims. (Cl. 75-3) This invention relates to a method and apparatus forcontrolling the temperature of rolls used in briquetting hot materials.

Although our invention has broader application, its principles applyparticularly to cooling the rolls of a press used for briquetting hotiron ore fines. A typical process for briquetting these fines involvesheating them to a temperature of about 1300 .to 2100 F. in .a rotarykiln or traveling grate, and pressing them into briquettes while theystill approach this temperature. The resulting briquettes are hard anddense and furnish excellent material for charging to a blast furnace orfor open hearth charge ore. The roll-type press commonly used in theprocess includes a pair of cylindrical roll bodies which have matingpillow-shaped pockets in their circumferential surfaces. The pressuresrequired are in the range of about 20,000 to 120,000 pounds per inch ofelfective roll width. The heat, pressure, and abrasive action of thematerial cause the roll surfaces to wear rapidly. Hence the rolls areshort-lived, even though their wearing surtaces usually are of hardalloy steels.

An object of our invention is to provide a method and apparatus forcontrolling the temperature of rolls used in briquetting hot materialsby applying a gaseous cooling medium to the rolls, and subsequentlyutilizing the heated medium to supply heat to the chamber where thematerials are heated preliminary to briquetting.

A further object is to provide a method and apparatus for cooling therolls of a briquetting press by applying air thereto in quantitiescontrolled to maintain the roll temperature within a predeterminedrange, and subsequently utilizing this air as preheated combustion airin the chamber where the materials are heated.

A more specific object is to provide a roll-cooling apparatus whichincludes a hood shaped to cover approximately half the circumferentialsurface of a roll without interfering with the function of the roll,means for injecting streams of cooling air into the hood against theroll surface, and control means for regulating the air volume tomaintain the temperature of the roll surface within a predeterminedrange.

In the drawing:

FIGURE 1 is a diagrammatic view of a hot-briquetting installationequipped with our temperature control apparatus;

FIGURE 2 is a partly diagrammatic end elevational view on a larger scaleand with parts broken away showing rolls equipped with our temperaturecontrol apparatus; and

FIGURE 3 is a horizontal section on line TIL-HI of FIGURE 2.

FIGURE 1 shows a heating chamber 10, illustrated as a conventionalrotary kiln. We continuousuly introduce fines (for example minus /2inch, minus /8 inch, or minus /41 inch iron ore) to the left end ofchamber .10 through a conventional feeding device 12. The right end ofthe chamber is equipped with a burner 13 to which we introduce fuel andprimary combustion air via pipes 14 and 15 respectively. heat the tinesto a suitable briquetting temperature, which in the example of iron oreis about 1500 to 1800" F. We hold the fines at this temperature longenough to drive oh all free and combined moisture, which may In thismanner we hi h??? Patented July 6, 1965 require about 15 minutes. Wastegases discharge from the left end of the chamber through a conventionalflue 16 and stack 17. Hot fines discharge continuously from the rightend of the chamber through an insulated chute 18 to a conventionalroll-type briquetting press 19, which forms them into briquettes whilestill hot, as already explained. A series of conveyors 2t) and 21receive the briquettes and accompanying fines and continuously carrythem to the entry port 22 at the top of a cooling shaft 23.

In the installation illustrated, we blow air through the briquettes andfines in shaft 23 from a blower 24 connected to the lower portion of theshaft, and thus cool the briquettes to a suitable handling temperature.The cooled briquettes discharge continuously from the bottom of theshaft to suitable handling equipment, such as a conveyor 25. The airalso has sufiicient velocity to pick up most of the unbriquetted finesbelow a predetermined particle size. Contact With the hot briquettes ofcourse heats the air, and it reaches a temperature about to 300 F. belowthe temperature at which briquettes enter the shaft. Heated air andentrained fines discharge continuously from the upper portion of theshaft through a pipe 26. The shaft is equipped with a suitable valve 27,such as a star feeder, to prevent escape of air through its entry port22. Pipe 26 discharges the air and entrained fines into the heatingchamber '10 beyond the flame 28 issuing from burner 13. Thus we utilizethe heated air as secondary combustion air, While We recycle the finesonly through the final portion of the heating chamber and subsequentapparatus. Air from the cooling shaft is not suitable as primarycombustion air in burners presently available for the reason that thelarge content of entrained fines would clog the burners. The foregoingmethod and apparatus for handling the unbriquetted fines and returningthem to the heating chamber, along with preheated secondary combustionair, form the subject of a separate application filed by the co-inventorRohaus, Serial No. 122,894, filed July 10, 1961 (now Patent No.3,116,996), and hence are not claimed in the present application.

In accordance with the present invention, we mount stationary hoods 29over the outer portions of the rolls of the briquetting press 19. Asbest shown in FIG- URES 2 and 3, we form each hood of a sheet metalshell which has an open side facing the br-iquetting roll andapproximately semicircular cutout-s in its end walls :to accommodate theroll. We fix sealing strips 36 of asbestos or equivalent around theedges of the cutouts and contacting the roll surface. We inject streamsof compressed air into each hood 29 via a plurality of fan-shapednozzles 31 directed against the surface of the roll and connected via apipe 32 to an air compressor 33. A pipe 34 carries air from the hoodback to burner 13 to supplement the air introduced to the burner viapipe 1 5 (FIGURE 1). Contact with the hot fines of course heats therolls, but the air streams from the nozzles impinge on the roll surfacesto maintain the rolls at a lower temperature. At the same time the airis heated, and is used advantageously as preheated combustion air in theheating chamber '10. Since the air does not pick up any appreciablevolume of fines in the hoods, we can use it as primary combustion air inthe burners, as illustrated. Nevertheless it is apparent we could usethis air as secondary combustion air the same as air from the coolingshaft 23.

We maintain the surface temperature of the rolls within a predeterminedrange in the region which is about to contact the hot fines. Preferablywe equip the apparatus with automatic control means for this purpose.The control means illustrated includes a temperature-sensing a element35, a controller 36, an adjustable valve 37 in pipe 32, and a motor 38for positioning valve 37, duplicated for each hood and roll. We positionthe temperature sensing elementSS adjacent the surface of the roll whereit emerges from hood 29 and connect this element with the controller 36and connect the controller in turn with motor 33. When the rolltemperature tends to change, the controller automatically energizes themotor to adjust valve 37. Adjustment of the valve increases ordiminishes the air volume as needed to maintain the roll temperaturewithin the desired range. We have not use their Modutrol valve anddamper motor described" in their Catalog ClOl-la. Each of the foregoingcatalogs is a printed publication, copyright 1960. Nevertheless it isapparent we can use equivalent devices from other suppliers.

Preferably the region of the roll surface about to contact the hot fineshas a temperature within the range 500 to 550 R, which We can vary byadjusting the controller 36. If the roll is not cooled, its surfacetemperature remains about 700 F. It is critical that we use a gas, suchas air, as the cooling medium rather than a liquid. If we used a liquidmedium, unevaporated liquid remaining in the pockets of the briquettingrolls would explode on contact with hot ore. Furthermore alloy 7 steelsof which the roll surfaces usually are formed cannot withstand thethermal shocks incident to liquid cooling. As a specific example todemonstrate how our invention operates, we heated a minus A1, inchhematite ore to about 1800 'F. and fed the ore at this temperature to abriquetting press having rolls 20 inches in diameter. Each roll wasconstructed with a Type 440A stainless steel sleeve having a single rowof fifty 1 /2 by 1% by A inch pillow-shaped pockets; the pockets wereseparated by inch lands. We spring-loaded the rolls in the usual mannerto provide a pressure at the roll bite of about 120,080 pounds perlinear inch of roll width. With the apparatus illustrated,'we blew airon the face of one roll opposite the bite to maintain a surfacetemperature of 550 F. in the region about to contact the hot fines,leaving the other roll uncooled. The life of the cooled roll was about50 percent greater than that of theuncooled roll. The heat recoveredfrom the roll and used as primary combustion air constituted a heatingvalue of about 88 B.-t.-u. per pound of air, which reduced the fuelrequirement of the burner about 4 percent.

While We have shown and described only a single embodiment of theinvention, it is apparent that modifica tions may arise. Therefore, wedo not Wish to be limited to the disclosure set forth but only by thescope of the appended claims.

We claim:

1. In a briquetting process in which fines are heated to an elevatedtemperature in a heating chamber and the heated fines are formed intobriquettes in a roll-type press, the combination therewith of a methodof controlling .the temperature of the briquetting rolls' comprisingimpinging air streams against the roll surfaces opposite the regionwhere the rolls contact the hot fines, thus cooling the roll surfacesand heating the air, and utilizing the heated air in the heating chamberas preheated combustion air. V 1 i 2.. In a briquetting process 'inwhich fines feed to a heating chamber and pass continuouslytherethrough, fuel burns with combustion air in said chamber to heat thefines to an elevated temperature, and the hea-ted'fines are formed intobriquettes in a roll-type press, the combination therewith of a methodof controlling the temperature of the briquetting rolls comprisingimpinging air streams against the roll surfaces opposite the regionwhere the rolls contact the hot fines, regulating the volume of air insaid streams to maintain the region of the roll surfaces about tocontact the hotfines at a temperature within a predetermined range,heating the air of said streams while cooling the rolls therewith, andconducting the heated air to the chamber for use as preheated combustionair.

3. In a briquetting proces in which iron ore fines feed to a heatingchamber and pass continuously therethrough, fuel burns with combustionair in said chamber to heat the fines to a temperature of about 1300 to2l00 F, and the heated fines are formed into briquettes in a roll-typepress, the combination therewith of a method of controlling thetemperature of the briquetting rolls comprising impinging air streamsagainst the roll surfaces oppo site the region Where the rolls contactthe hot fines, regulating the air volume to maintain the region of theroll surfaces about to contact the hot fines at a temperature within arange of 500 to 550 F, heating the air of said streams while cooling therolls therewith, and conducting the heated air to the chamber for use aspreheated combustion air; i

4. In a briquetting installation which includes a heating chamber, meansfor feeding fines to said chambena burner in said chamber forburning'fuel with combustion air, a roll-type briquetting press, andmeans for continuously transferring heated fines from said chamber tosaid press, the combination therewith of an apparatus for controllingthe temperature of the rolls of said press, said apparatus comprisingmeans for impinging air streams against the roll surfaces opposite theregion where the rolls contact the hot fines,-and means for conductingthe air from said streams to said chamber to be used as preheatedcombustion air. 5. In a briqnetting installation which includes aheating chamber, means for feeding fines to said chamber, a burner insaid chamber for burning fuel with combustion air, a roll-typebriquettingpress, and means for continuously transferring heated finesfrom said chamber to said press, the combination therewith of anapparatus for controlling the temperature of the rolls of said press,said apparatus comprising means for impinging air streams against theroll surfaces opposite the region where the rolls contact the hot fines,means for regulating the volume of air in said streams to maintain theregion of the roll surfaces about to contact the hot fines at atemperature within a predetermined range, and means for conducting theair from said streams to said chamber to be used as preheat-edcombustion air.

6. In a briquetting installation which includes a heating chamber, meansfor feeding fines to said chamber, a

burner in said chamber for burning fuel with combustion air, a roll-typebriquetting press, and means for continuously transferring heated finesfrom said chamber to said press, the combination therewith of anapparatus for controlling the temperature of the rolls of said press,said apparatus comprising hoods covering the portions of the rollsurfaces opposite the region Where the rolls contact the hot fines,means for injecting air streams against the roll surfaces Within saidhoods, and pipe means connecting said hoods and said chamber forconducting the air from said hoods to said chamber to be used aspreheated combustion air. a

7. In a briquetting installation which includes a heating chamber, meansfor feeding fines to saidchamber, a burner in said chamber for burningfuel with combustion air, a roll-type briquetting press, and'means forcontinuously transferring heated fines from said chamber to said press,the combination therewith of an apparatus for controlling thetemperature of the rolls of said press, said apparatus comprising hoodscovering the portions of the roll surfaces opposite the region where therolls contact the hot fines, said hoods having open faces directedtoward the rolls, means for injecting air streams against the rollsurfaces within said hoods, means for regulating the volume of air insaid streams to maintain the region of the roll surfaces about tocontact the hot fines at a temperature Within a predetermined range, andpipe means connecting said hoods and said chamber for conducting the airfrom said hoods to said chamber to be used as preheated combustion air.

8. In a briquetting installation which includes a heating chamber, meansfor feeding fines to said chamber, a burner in said chamber for burningfuel With combustion air, a roll-type briquetting press, and means forcontinuously transferring heated times from said chamber to said press,the combination therewith of an apparatus for controlling thetemperature of the rolls of said press,

said apparatus comprising hoods covering the portions of the rollsurfaces opposite the region where the rolls contact the hot fines, saidhoods having open faces directed toward the rolls, nozzles mounted insaid hoods and directed at the roll surfaces, pipe means connected tosaid nozzles for introducing compressed air thereto and therebyinjecting air streams against the roll surfaces within said hoods,valves in said pipe means, means adjacent the rolls Where their surfacesemerge from said hoods for sensing the temperature of the rolls, acontroller oper-atively connected to said last named means and saidvalves for adjusting the Valves and thereby regulating the volume of airin said streams to maintain the region of the roll surfaces about tocontact the hot fines at a temperature Within a predetermined range, andpipe means connecting said hoods and said chamber for conducting the.air from said hoods to said chamber to be used as preheated combustionair.

References Cited by the Examiner UNITED STATES PATENTS 1,994,721 3/35Lorig et al 80-41 1,996,500 4/35 Adams 80-41 2,833,642 5/5-8 Barker etal -3 2,958,596 11/60 Purvance 753 BENJAMIN HENKIN, Primary Examiner.DAVID L. RECK, Examiner.

1. IN A BRIQUETTING PROCESS IN WHICH FINES ARE HEATED TO AN ELEVATEDTEMPERATURE IN A HEATING CHAMBER AND THE HEATED FINES ARE FORMED INTBRIQUETTES IN A ROLL-TYPE PRESS, THE COMBINATION THEREWITH OF A METHODOF CONTROLLING THE TEMPERATURE OF THE BRIQUETTING ROLLS COMPRISINGIMPINGING AIR STREAMS AGAINST THE ROLL SURFACES OPPOSITE THE REGIONWHERE THE ROLLS CONTACT THE HOT FINES, THUS COOLING THE ROLL SURFACESAND HEATING THE AIR, AND UTILIZING THE HEATED AIR IN THE HEATING CHAMBERAS PREHEATED COMBUSTION AIR.